Tennis racket sensor system and coaching device

ABSTRACT

Embodiments of the present invention are directed to devices, systems, and methods for measuring values obtained from one or more sensors installed on a player&#39;s tennis racket and/or worn on the player&#39;s body, and using those values to calculate various parameters, such as the physical position and motion of the tennis racket. Embodiments may translate the parameters and derive one or more occurrences corresponding to phases of a tennis point or drill and then generate real-time audible, visual, and/or haptic coaching prompts and other related commands and signals, for the purpose of improving a player&#39;s motor skills. Embodiments may also send and receive messages to/from other embodiments, thereby permitting a player to interact with other players, coaches, or devices, such as ball machines and cameras.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. patentapplication Ser. No. 15/928,302, entitled “Tennis Racket Sensor Systemand Coaching Device,” filed Mar. 22, 2018; which claims priority to U.S.patent application Ser. No. 14/697,248, entitled “Tennis Racket SensorSystem and Coaching Device,” filed Apr. 27, 2015 and issued as U.S. Pat.No. 9,956,469 on May 1, 2018; and U.S. Provisional Patent ApplicationNo. 62/084,205, entitled “Tennis Racket Sensor System,” filed Nov. 25,2014, the entire contents of each of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention is related to the field of athlete performancemonitoring, athletic training, and coaching. More particularly, thepresent invention is related to the field of athlete performancemonitoring, athletic training, and coaching within racket sports, e.g.,the sport of tennis. Even more particularly, the present invention isrelated to devices, systems, and methods for sensing certain parametersrelating to the motion of a racket, paddle, or club while receiving andprocessing event messages generated by other devices, and providingaudible, visual, and/or haptic feedback, coaching prompts, and/orinstructions.

BACKGROUND

It is well known in the sporting world that athletes are often intenselyinterested in improving their performance in a given sport. Thisobservation is true for all levels of athletes, but it may be especiallytrue for novice athletes who are just learning a new sport or a newskill. Some athletes learn new skills by trial and error. Other athletesreceive the benefit of a trainer or instructor. Regardless of whichlearning process is employed, most athletes tend to go through threestages of motor skill acquisition when they are learning or improvingtheir skills: a cognitive stage, an associative stage, and an autonomousstage.

In the cognitive stage, an athlete begins to acquire information abouthow to perform a new skill. The focus of the cognitive stage is thedevelopment of a mental model of movement. The athlete receives andprocesses new information relating to a skill and then processes thatinformation in an attempt to cognitively understand the essentialrequirements and parameters of motor coordination. The cognitive stageis characterized by large gains in performance, but the performance istypically inconsistent. To improve performance consistency at thisstage, techniques such as slow-motion drills, video analysis, andaugmented feedback can be highly effective. It is especially importantthat the athlete be provided with the necessary information, guidance,and time to establish sound fundamentals of movement through cognitiveprocesses.

In the associative stage, the learning process becomes less cognitiveand more physical, as an athlete attempts to apply what he/she haslearned. Here, the athlete attempts to translate cognitive knowledgeinto procedural knowledge. In other words, the athlete tries totransform his/her understanding about what to do into the motorknowledge of how to do it. Accordingly, there is less emphasis onprocessing new information at the associative stage. Instead, theathlete uses conscious processing, combined with performance feedback,to obtain better motor control. The athlete may also work at makingsmall adjustments to various movements and stringing together shortsequences of smaller movements.

In the final autonomous stage of motor acquisition, typically afteryears of training, physical performance can become largely automatic.Cognitive processing demands are greatly reduced, and athletes can becapable of attending to and processing other information, such as theposition of opponents, game strategy, and a particular form or style ofmovement. This is the stage where athletes can respond almostreflexively, where they can “grip it and rip it,” where they look andautomatically react, and where they can enter a “zone” to achieve astate of flow.

Both good outcomes and bad outcomes are associated with the autonomousstage. Good outcomes are based on the fact that motor performance atthis level requires much less cognitive demand, which thereby frees anathlete to engage in secondary tasks. On the other hand, when cognitivedemand is lower, there can be more room for irrelevant and distractingthoughts. Another bad outcome during automatic motor performance is thatan athlete may perpetuate incorrect movements. Just because a motormovement can be performed automatically does not mean the movement iscorrect or worthy of being maintained. Moreover, as soon as athletesstop thinking about a movement that was learned during the cognitive andassociative stages, they may revert back to old and incorrect autonomousmotor movements during competition or when they are under stress or arefatigued.

Indeed, there is always room for athletic improvement. This is true forall sports and all ages. Highly successful athletes and highly effectivecoaches are always looking for ways to get better. Consequently, theyfrequently revisit both the cognitive and associative stages of motorlearning. Revisiting these stages can be essential for refining andperfecting athletic movements.

In the sport of tennis, for example, it is necessary to learn not onlythe rudimentary movements required to hit a ball, but also to quicklyrecognize, react, and respond to the movements of an opposing player.(The terms “athlete” and “player,” as used herein, are intended to havethe same meaning.) Indeed, an ability to recognize and react to anopponent's shot can determine whether a player is able to get inposition to hit a ball, able to hit a weak defensive shot, or able tohit a strong winning shot.

A quick reaction to the movements of an opposing player can depend on anability to anticipate, and the ability to anticipate can depend on anability to read cues from an opposing player. Recent research has shownthat one of the differences between an expert and a novice tennis playeris where a player is looking (i.e., directing his/her attention) when anopponent hits the ball. In addition to a player's focus of attention,proficiency in tennis also depends on a player's efficiency of movement.Players and coaches can use many drills to improve movement efficiency.Drills can also help to train player attention and focus through properanticipation, observation, and identification of an opponent'smovements.

Without the aid of a coach it is often difficult for a player to beconsistently alerted about incorrect movements or improper preparation.A player typically cannot observe their own movements and must rely onoutcomes to judge whether a particular movement requires adjustment. Incontrast, a third party observer, such as a coach, can observe andanalyze a player's movements as they occur independent of the outcomeachieved and therefore are able to provide feedback to the playerquickly after the incorrect movement occurs. However, even if coachesare utilized, they must rely on their individual comprehension of propermovements and preparation to judge their observations of a player toprovide appropriate corrective feedback. Because both comprehension andobservation can vary from person-to-person, corrective feedback receivedfrom coaches can be highly subjective and inconsistently provided to theplayer, therefore detracting from the efficiency of the player's motorskill acquisition.

Additionally, such corrective feedback is limited to verbal commands orengaging a player in visual response drills, neither of which require anathlete to react to an actual opponent. Training drills of this type arenot efficient at providing immediate feedback to a player. As a result,the training benefit of such drills is not as high as it could be ifappropriate feedback and cue instruction could be supplied in real time.

Various devices in the prior art help to provide athletes with feedbackabout their motor movements. U.S. Pat. No. 5,681,993 discloses aplurality of force sensors disposed at predetermined pressure pointsbetween a human hand and a golf club. A conversion device transformsinputs from the force sensors into audible sound frequencies that varyin proportion to the force applied and the location of the force. Theconversion device also transforms the force sensor inputs into vibratoryoutputs or electrical currents that vary in proportion to the forcelevel and location of the force. The outputs can be useful to determinewhether a club is being held correctly or if too much force is beingapplied to one portion of the club handle.

U.S. Pat. Nos. 5,439,217 and 5,439,216 each disclose a device thatinforms a player when a proper grip is being applied to a racket handleor golf club. The device utilizes a membrane switch that is connected toa portable power source and coupled to an audible alarm, which isactivated when the switch closes. The alarm indicates when an excessivehandle grip force is being applied to the handle.

U.S. Pat. No. 5,221,088 discloses a sports training aid having a pair offoot sensors that produce measurement signals corresponding to theweight applied to each foot sensor. The training aid compares themeasurement signals with a specified range of values and producesaudible sounds indicative of the relationship between the measurementsignals and the specified range of values. The audible sounds providethe user with immediate feedback regarding shifts in weight.

U.S. Pat. No. 6,134,965 discloses a device for measuring the strikevelocity of a tennis ball, where the device is installed on the tennisracket and measures the force exerted on the tennis racket stringsduring a ball strike. After a ball strike, the device displays ameasured value associated with a calculated ball velocity.

There are additionally a variety of measuring devices for a strikingelement such as a racket or a golf club that are designed to measure theforce with which a ball is struck or to measure the point of impact of aball on the striking element. These devices are described in thefollowing publications DE-A-34 36 218, U.S. Pat. Nos. 4,991,850,4,870,868 and 4,008,324.

Some companies are developing devices that measure and record anathlete's movements during a tennis match. As an example, an Australiancompany called Smash Wearables Pty. Ltd. (seehttp://www.smashwearables.com) has developed a lightweight band that anathlete can wear on the wrist. The band, called “Smash,” uses onboardsensors to transmit movement information to an application running on aSmartphone. The sensors measure specific physical values associated withmovement of the athlete's wrist. The Smartphone application records thesensed physical values and calculates information about the movement ofan implied (not directly connected) tennis racket. The calculatedinformation can include racket speed, racket angle, racket momentum, theangle of wrist rotation, and the racket stroke trajectory. Based on thecalculated information about the movement of a player's wrist, theSmartphone application can also infer a number of other attributesassociated with a player's performance in a tennis match, including thenumber and type of shots (e.g., forehand versus backhand and topspinversus backspin), statistics about the amount of spin delivered acrossshots, and the consistency of racket placement at the point of impactwith a tennis ball. Using the Smartphone application, an athlete can setcertain performance goals and track progress toward those goals.

Similarly, the well-known tennis racket company, Babolat, sells a racketcalled the “Babolat Play Pure Drive” (see http://en.babolatplay.com/)which includes sensors integrated into the handle of the racket. Thesensors measure and record information regarding power, impact location,and type and number of strokes. The information is stored in memory andlater retrieved, analyzed, and presented to the user with a Smartphoneapplication connected via USB or Bluetooth.

SUMMARY OF THE INVENTION

This brief summary is provided to introduce certain concepts in asimplified form that are further described below in the DetailedDescription of the Embodiments. This brief summary is not intended toidentify key features or essential features of the claimed subjectmatter, nor is it intended to limit in any way the scope of the claimedinvention.

Embodiments of the present invention are directed to devices, systems,and methods for measuring values obtained from one or more sensorsinstalled on a player's racket, paddle, or club (hereinafter, referencewill generally be made to a “racket”), and/or worn on the player's body,and using those values to calculate a number of parameters, includingthose related to the physical position and motion of the racket.Embodiments of the present invention are also directed to devices,systems, and methods for receiving messages generated by other devices,including other embodiments of the present invention that are installedon rackets or worn on the bodies of other players. Embodiments of thepresent invention correlate the parameters and messages to generatereal-time audible, visual, and/or haptic coaching prompts and otherrelated commands and signals, for the purpose of improving certain motorskills associated with the corresponding sport.

In one embodiment, a device including a processor and one or moresensors is installed on a player's racket and/or on an article worn bythe player. As the player swings the racket, the device measures valuesobtained from the one or more sensors and calculates various parametersassociated with the racket's physical position and motion, includingvarious angle measurements of the racket with respect to its position inspace, the direction of motion, speed of motion, acceleration,vibration, and shock. The various parameters associated with a racket'sphysical position and motion may be further processed to determine whencertain events have occurred or are in the process of occurring. Theseevents can include forehand preparation, backhand preparation, overheadpreparation, forehand swing, backhand swing, overhead swing, contactwith a tennis ball, contact with another object (such as the net, theground, or a player's body), and the application of spin to the ball.From such events, the embodiment can further derive one or more phasesof a point or drill (such as serving, rallying, or ending a point).

Embodiments of the invention can determine if a racket has made contactwith a ball and subsequently provide feedback to the player, for exampleas an audible alert or voice prompt emitted from the device or aconnected peripheral. The invention can also transmit messages to otherembodiments of the invention to trigger feedback in those embodiments.Further, the invention can transmit messages to a variety of peripheralsto trigger other actions, such as triggering a ball machine to launch aball or triggering a camera to capture a photo.

In one example, an embodiment of the invention can be used in asingle-user mode where an audible alert or voice prompt is issued afterthe device detects a ball impact on the racket. A player can set acustom time delay (e.g., 1.5 seconds) between the moment of ball impactand the audible alert. Feedback provided to the player can indicate whenthe player should look up from the ball impact point. This featuretrains the player to concentrate on the ball impact point on the racketand avoid a natural tendency to look up at the expected trajectory ofthe ball after impact, which pulls the shoulders and head forward and upprematurely, potentially causing a suboptimal hit.

While measuring and processing parameters relating to the physicalposition and motion of a racket, embodiments of the present inventionmay also be used in a multi-player mode. Such embodiments receive andprocess messages generated by other embodiments of the invention (forexample, embodiments used by an opponent), and issue audible coachingprompts to a player, in real time, under certain pre-programmedconditions, with the goal of improving the player's performance byrevisiting the cognitive and associative stages of motor learning and byconditioning and reinforcing specific physical behaviors throughrepetition. For example, the feedback can indicate when the playershould make a specific action, for example to assess his/her level ofpreparedness or to move his/her body and racket to a ready position suchas a “split step” position. The prompt can also warn a player when toprepare for a backhand or a forehand shot. This feature trains theplayer to prepare earlier and make use of the full amount of timeavailable between volleys. The audible coaching prompts can includesounds, such as beeps or other tones, as well as prerecorded orsynthesized verbal instructions. The prompts can be provided directly tothe player or to another player or observer via wireless communications.

In another example, a message transmitted by an embodiment of theinvention can be received by an embodiment connected to or integratedwithin a ball machine. Such a message can trigger the ball machine tolaunch a new ball. The timing of the launch can be similar to a returnshot from a real player, thereby simulating a more realistic environmentduring practice. The embodiment connected to or integrated within theball machine can also send messages to other embodiments, such messagesincluding information about the launch, including power, spin, anddirection. This information enables the other embodiments to generatefeedback that is appropriate for the particular situation.

Finally, in still another example, a message transmitted by anembodiment of the invention can be received by other external devices.For example, a camera can receive messages from the embodiment thatinstruct the camera to take a photo, a series of photos, or a videoimmediately upon receiving the message or a user-adjustable time afterthe message is received. The resulting pictures or videos can then beused retrospectively to analyze and improve a player's preparation andexecution.

Over time and through repetition, the varied timing prompts provided byembodiments of the invention should help to improve the player's skilllevel by training the player to become better at recognizing certainopponent behaviors, to improve the performance of certain movements, andto reinforce the timing and execution of various combinations ofmovements in reaction to those of a vigorous opponent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a tennis racket installed with an exemplaryembodiment of a device for sensing racket motion parameters andproviding feedback in accordance with the present invention.

FIG. 1B illustrates a wearable device installed with an exemplaryembodiment of a device for sensing racket motion parameters andproviding feedback in accordance with the present invention.

FIG. 1C illustrates a ball machine installed with an exemplaryembodiment of a device for triggering the ball machine to launch ballsin response to events detected at a racket in accordance with thepresent invention.

FIG. 2 is a block diagram of certain internal components of an exemplaryembodiment of a device for sensing racket position and motion parametersand providing feedback in accordance with the present invention.

FIG. 3 is a flow chart that is representative of an exemplary embodimentof a finite state machine for associating events detected at a racketwith phases of a point or drill.

FIG. 4 is a flow chart that is representative of an exemplary embodimentof a finite state machine for associating events detected at a racketwith phases of a point or drill.

FIG. 5A illustrates an exemplary single-user embodiment of a method forproviding feedback in accordance with the present invention.

FIG. 5B illustrates an exemplary multi-user embodiment of a method forproviding feedback in accordance with the present invention.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described with reference tothe accompanying drawings, wherein like parts are designated by likereference numerals throughout, and wherein the leftmost digit of eachreference number refers to the drawing number of the figure in which thereferenced part first appears. The terms “player” and “user” are usedinterchangeably throughout the description, and both should generally betreated as a user of the present invention.

FIG. 1A is a view of a tennis racket installed with an embodiment of adevice for sensing racket position and motion parameters and providingfeedback in accordance with the present invention. The embodimentprovides a coaching device 100 installed on a tennis racket 102. Asillustrated, coaching device 100 is installed in the throat 104 oftennis racket 102, i.e. in the opening between the two beams of theracket that extend from the handle 106 to the head 108. Coaching device100 can be attached to any part of racket 102 in a variety of waysincluding, for example, through the use of one or more clips, bolts,straps, bands, clamps, magnets, adhesives, or a combination thereof. Inan embodiment, coaching device 100 includes a body constructed of asuitably strong but lightweight material (e.g., plastic or aluminum),and the body houses a plurality of components described in furtherdetail below. Coaching device 100 can also be embedded within racket102. For example, coaching device 100 can be embedded within handle 106.Alternatively, if the throat of tennis racket 102 is a solid component,coaching device 100 can be embedded within the solid throat.

FIG. 1B is a view of a wearable accessory 110 installed with anotherembodiment of the present invention. The embodiment provides coachingdevice 100 installed on (e.g., via one or more clips, bolts, straps,bands, clamps, magnets, adhesives, or a combination thereof) or embeddedwithin wearable accessory 110. Wearable accessory 110 can be any sort ofaccessory that is wearable on a player's hand or wrist, for example abracelet, wristband, or glove. Wearable accessory 110 can be made of anysuitable material, including textile, leather, metal, plastic, rubber,wood, or a combination thereof.

FIG. 1C is a view of a ball machine 116 installed with anotherembodiment of the present invention. The embodiment provides coachingdevice 100 connected to ball machine 116 via wired or wireless meansaccording to well-known connection methods. Coaching device 100 can alsobe integrated within ball machine 116. In such an embodiment, coachingdevice 100 can share one or more components with ball machine 116, forexample the ball machine's power supply. Ball machine 116 can be anytype of ball machine, for example a tennis ball machine, a table tennisball machine, or a baseball or softball pitching machine. These andother embodiments will be described in further detail below.

FIG. 2 is a block diagram of an exemplary embodiment of coaching device100 in accordance with the present invention, which in certain operativeembodiments can be installed on a racket 102 as illustrated in FIG. 1A,installed on a wearable accessory 110 as illustrated in FIG. 1B, orinstalled on a combination of the two. In such a combination, forexample, some components may be installed on the racket 102, othercomponents may be installed on the wearable accessory 110, and thecomponents may share information via wireless communications. In theembodiment of FIG. 2, coaching device 100 comprises numerous components,including one or more interface(s) 202, one or more sensor(s) 204, oneor more processor(s) 206, one or more memory(ies) 208, one or moretransceiver(s) 210, one or more power module(s) 212, and instructionsand logic 214.

Interface 202 may comprise one or more devices for receiving input orproviding output. Interface 202 can include one or more digitaldisplay(s) for outputting a text-based or graphical user interface andfor receiving user input, for example via a touchscreen component.Interface 202 can also include one or more physical buttons, scrollwheels, or other conventional devices for receiving user input. In anembodiment, a player may use interface 202 to configure coaching device100, toggle power, adjust volume, switch between various modes ofoperation, review metric data, and otherwise interact with coachingdevice 100.

In an embodiment, interface 202 includes a microphone for receivingvoice commands or messages. A player may, for example, use voicecommands as an alternative to or in addition to using a digital displayand/or buttons for interacting with coaching device 100. A microphonemay also be used to record voice messages that may be sent to otherembodiments of the invention.

Interface 202 may comprise one or more devices for providing coachingfeedback to the player. For example, interface 202 can include one ormore light(s) (e.g., light emitting diodes) for providing visualfeedback and/or one or more loudspeaker(s) for providing audiblefeedback. Interface 202 may also comprise one or more vibration motorsfor providing haptic feedback to the player. For example, a vibrationmotor like those typically found in modern mobile phones may beinstructed to vibrate or “rumble” to remind a player to recover andprepare for the next shot. In embodiments, coaching feedback may beprovided by any combination of one or more of the feedback devicesdisclosed herein.

Sensor 204 may comprise one or more device(s) for detecting andmeasuring a variety of physical parameters associated with coachingdevice 100. For example, sensor 204 can include one or moreaccelerometer(s) for measuring one or more of the orientation,coordinate acceleration, vibration, and shock affecting coaching device100. Sensor 204 can include any type of sensor that is capable ofdetecting and/or measuring physical/spatial parameters, includingvibration, acceleration, and direction of motion. For example, agyroscope may be used instead of or in addition to an accelerometer tomeasure the orientation of coaching device 100.

Processor 206 may comprise one or more devices for executingmachine-readable instructions that perform one or more predeterminedtasks. Processor 206 can comprise any one or a combination of hardware,firmware, and/or software. In general, processor 206 can utilizemechanical, pneumatic, hydraulic, electrical, magnetic, optical,informational, chemical, and/or biological principles, signals, and/orinputs to perform tasks. In certain embodiments, processor 206 can actupon information by manipulating, analyzing, modifying, converting, ortransmitting the information for use by an executable procedure and/oran information device, and/or routing the information to an outputdevice. Processor 206 can function as a central processing unit, localcontroller, remote controller, parallel controller, and/or distributedcontroller, etc. Processor 206 can include a general-purpose device,such as a microcontroller and/or a microprocessor. In certainembodiments, processor 206 can be a dedicated purpose device, such as anApplication Specific Integrated Circuit (ASIC) or a Field ProgrammableGate Array (FPGA) that has been designed to implement in its hardwareand/or firmware at least a part of an embodiment disclosed herein.

Memory 208 can be any type of apparatus known in the art that is capableof storing analog or digital information such as instructions and/ordata. Examples include a non-volatile or read only memory (“ROM”),volatile or random access memory (“RAM”), flash memory, various types ofmagnetic media, and the like. Memory 208 can be coupled to one or moreprocessor(s) 206 and can store instructions and logic adapted to beexecuted by one or more processor(s) 206, as according to any of theembodiments disclosed herein.

Transceiver 210 may comprise any device, system, subsystem, or componentcapable of wirelessly transmitting and/or receiving information,particularly messages sent to or received from other coaching devices100 in accordance with embodiments of the present invention. Forexample, transceiver 210 can include a cellular radio, RF transceiver,Bluetooth transceiver, WiFi transceiver, wireless broadband transceiver(WiMAX), ZigBee transceiver, or other similar capability.

Transceiver 210 may also receive input and provide output or feedback toone or more external device(s), including ball machines, cameras,headsets, computers, tablets, mobile phones, memory sticks, and otherelectronic devices. For example, transceiver 210 can provide output to acamera, the output triggering the camera to record a picture or videocorresponding to an event occurring on coaching device 100. In anotherexample, transceiver 210 can provide output to and receive input from amobile phone, wherein the mobile phone permits a player to review metricdata recorded by coaching device 100 and configure coaching device 100.The connection between transceiver 210 and an external device can bewireless or wired. For wired connections, transceiver 210 can includeone or more port(s) accessible on or within the housing of coachingdevice 100.

Power module 212 may comprise one or more devices for providingelectrical power to the other components of coaching device 100. Powermodule 212 may include one or more battery cells (e.g., lithium,alkaline, or NiMH battery cells) or other power supplies, any number ofwhich can be electrically connected together. Some or all of the batterycells may be rechargeable. Power module 212 may also include a powerinput to receive input power from a power source, and a power output toprovide output power to a load. In an embodiment, power module 212stores kinetic energy captured from the motion of coaching device 100 aselectricity in one or more battery cell(s) and/or capacitor(s).

Instructions and logic 214 may comprise directions adapted to cause amachine, such as coaching device 100, to perform one or more particularactivities, operations, or functions. The directions, which cansometimes form an entity called a “kernel”, “operating system”,“program”, “application”, “utility”, “subroutine”, “script”, “macro”,“file”, “project”, “module”, “library”, “class”, “object”, or“Application Programming Interface,” etc., can be embodied as machinecode, source code, object code, compiled code, assembled code,interpretable code, and/or executable code, etc., in hardware, firmware,and/or software. Instructions and logic 214 may reside in processor 206,in memory 208, or in another specialized device or component.

For ease of illustration, other components common to electrical deviceshave been excluded from FIG. 2. For example, a communications buspermits each of the other components to communicate with each otheraccording to well-known techniques.

Having described the components of coaching device 100, attention willnow be paid to its operation. For purposes of this description,reference will be made to the following terms:

Physical Event: a measurable occurrence in the physical world (e.g., aswing of a racket or an impact with a ball). A Physical Event mayindicate the occurrence of one or more Tennis Events.

Tennis Event: a logical occurrence derived from one or more PhysicalEvents (e.g., the start of a point). A Tennis Event may trigger one ormore Notifications and/or Calculations.

Notification: an instruction to take some action corresponding to one ormore Tennis Events (e.g., an instruction to play a recorded voicemessage coaching the player to focus on the point of impact).

Calculation: an instruction to calculate and/or output one or moremetrics corresponding to one or more Tennis Events (e.g., an instructionto tally the number of shots in a rally).

As discussed above, coaching device 100 measures values obtained fromsensor 204 and calculates one or more physical parameters associatedwith coaching device 100. Coaching device 100 then translates theseparameters into one or more Physical Events. The translation process maybe specified by instructions and logic 214 and performed by processor206. More particularly, instructions and logic 214 may include one ormore tables that map certain parameters to one or more Physical Events.For example, parameters consistent with a forehand swing may map to onePhysical Event, while parameters consistent with striking a ball threetimes in quick succession may map to a different Physical Event.

A Physical Event may be any occurrence (or, in some embodiments, a pausebetween occurrences) that may be derived from measurements taken bysensor 204. For example, Physical Events can include an impact of theplayer's racket with a tennis ball, timed pauses between impacts,multiple closely spaced impacts, the number of steps between impacts, aphysical orientation of the racket, and an acceleration of the racket.

For purposes of illustration only, an embodiment is described thatincludes the following specific Physical Events: Local Impact (i.e., theplayer strikes the ball), Remote Impact (i.e., the player's opponentstrikes the ball), No Impact Swing (i.e., a swing and miss of the ball),First Pause (i.e., a pause long enough to indicate that a point orexchange has ended), Second Pause (i.e., a pause long enough after theFirst Pause to indicate that the next point or exchange is about tobegin), Triple Local Impact (i.e., the player is preparing to serve),and Triple Remote Impact (i.e., the player's opponent is preparing toserve). Other Physical Events may be contemplated by one of ordinaryskill in the art without departing from the scope of the invention,provided they can be mapped to one or more values and parameters.

From each Physical Event, coaching device 100 derives a correspondingTennis Event. A Tennis Event can include any distinct event that canoccur during a tennis point or drill (e.g., serve, shot, end of point,etc.). For purposes of illustration only, an embodiment is describedthat includes the following specific Tennis Events: Start of Exchange,My Serve, Opponent's Serve, My Shot, Opponent's Shot, and End ofExchange. Other Tennis Events may be contemplated by one of ordinaryskill in the art without departing from the scope of the invention.

As illustrated in Table 1, each Physical Event maps to at least oneTennis Event according to a logical correlation. In an embodiment, asingle Physical Event may map to different Tennis Events depending on anoperating mode of coaching device 100, such as a Drill Mode or a PointMode. For example, when Point Mode is operational, a Triple ImpactPhysical Event indicates that the player is about to begin his or herserve and therefore maps to a Start of Point Tennis Event. A player mayselect an operating mode by, for example, interacting with a graphicaluser interface and/or one or more physical buttons provided by interface202, or any other suitable means such as by issuing voice commands.

TABLE 1 Corresponding Tennis Event Physical Event Drill Mode Point ModeLocal Impact My Shot if first impact, My Serve, else My Shot RemoteImpact Opponent's Shot if first impact, Opponent's Serve, elseOpponent's Shot No Impact Swing End of Exchange End of Point First PauseEnd of Exchange End of Point Second Pause Start of Exchange Start ofPoint Triple Impact Start of Exchange Start of Point

Tennis Events drive a computerized model of a tennis drill or point. Inan embodiment, the computerized model may comprise a finite statemachine. A finite state machine (“FSM”) comprises a number of states,and the FSM is only ever in one state at a time (i.e., the “currentstate”). The FSM transitions from one state to another upon theoccurrence of a triggering event or condition. In an embodiment, eachstate in the FSM corresponds to a phase of a tennis drill or point, andthe occurrence of a Tennis Event causes the FSM to either transition toa different state or repeat the same state.

Each state in the FSM may further be associated with one or moreNotifications and/or one or more Calculations as defined above. In anembodiment, a Notification includes user-customizable coaching feedback.The coaching feedback can include audible feedback (e.g., tones,recorded voice messages, and/or other sound effects), visual feedback(e.g., textual or graphical messages and/or flashing LEDs), hapticfeedback (e.g., vibrations), or any combination of the above. Forexample, a variety of methods may be used to encourage a player to keephis or her eyes focused on the point of contact between the racket andthe ball. In an embodiment, a Notification includes switching on an LEDfor a short period of time with the occurrence of a My Shot Tennis Eventto remind the player to remain focused on the point of contact. In thesame or an alternative embodiment, a Notification includes playing arecorded voice message shortly after the occurrence of a My Shot TennisEvent, thereby reminding the player to stay focused on the point ofcontact during the next shot.

Any of a variety of recorded voice messages may be played as part of aNotification without departing from the scope of the invention. In anembodiment, the voice messages may be predefined and recorded by awell-known tennis professional, and/or the voice messages may berecorded by the player or the player's coach. Some example voicemessages may include the following: “Keep feet moving,” “Recover andsplit,” “Turn shoulders,” “Move through the shot,” and “Point to theball.”

A Calculation can be any instruction to calculate and/or output (e.g.,via a GUI or audible message) one or more metrics corresponding to oneor more Tennis Events. For example, metrics can include one or more ofthe following: number of shots in a rally or point, length of time of arally or point, transit time for a player's shot, time between shots,swing speed, power, number of steps between shots, and statisticalanalyses of any of the above (e.g., averages, totals, etc.). Othermetrics may be contemplated by one of ordinary skill in the art withoutdeparting from the scope of the invention.

For example, an End of Point Tennis Event may cause a Calculation thatoutputs the number of shots in the most recent point. A player may alsoreview metrics on demand, for example by using interface 202 to select aparticular Calculation.

In an embodiment, there may be different FSMs associated with differentoperating modes. For example, FIGS. 3 and 4 illustrate the phases of twoFSMs when coaching device 100 is operating in a Drill Mode and a PointMode respectively.

FIG. 3 illustrates FSM 300 for a Drill Mode embodiment. FSM 300 firstenters phase 302 (a ready state or starting state) with the occurrenceof a Start of Exchange (“SOE”) Tennis Event. Phase 302 may be associatedwith one or more Calculations and/or Notifications. For example, aCalculation may include setting a shot count value to zero, and aNotification may include outputting audible feedback instructing theplayer to assume a ready stance.

In the embodiment illustrated in FIG. 3, a Local Impact or Remote ImpactPhysical Event may trigger a corresponding My Shot or Opponent's ShotTennis Event, and thus cause FSM 300 to enter phase 304 (a rallyingstate). Like with phase 302, phase 304 may be associated with one ormore Calculations and/or Notifications. For example, a Calculation mayinclude incrementing a shot count, and a Notification may includeoutputting a recorded voice message instructing the player to maintain aneutral grip.

FSM 300 repeats phase 304 each time a My Shot or Opponent's Shot TennisEvent occurs at decision 306, and enters phase 308 (end of rally) if anEnd of Exchange (“EOE”) Tennis Event occurs at decision 306. Phase 308may also be associated with one or more Calculations and/orNotifications. For example, a Calculation may include outputting thetotal shot count, and a Notification may include audible feedbackoffering encouragement to the player, or there may be no correspondingCalculation or Notification at all. FSM 300 loops back to phase 302 withthe occurrence of an SOE Tennis Event.

In an embodiment, Calculations and Notifications are associated withphases of an FSM in a manner that is instructive and relevant to theplayer's actions. For example, it would be of little use to output anaudible Notification concerning a serve during a rallying phase.Calculations and Notifications may be configured to particular phases ofan FSM in a predefined manner, or the player may customize theconfigurations. Such configurations of Calculations and Notificationsmay be saved as Lesson Plans that are quickly selectable and modifiableby the player. In an embodiment, coaching device 100 includes a defaultlesson plan for each operating mode.

A Lesson Plan is a configuration of Calculations and Notifications. Inan embodiment, coaching device 100 may have one or more default LessonPlans and a player may create and edit his or her own lesson plans. Manydifferent embodiments of a Lesson Plan are contemplated by theinvention, but Table 2 illustrates a sample Lesson Plan, including aname, operating mode, voice selection, and a plurality of Calculationand Notification parameters and their corresponding Tennis Events.Lesson Plans may also include a variety of other parameters.

TABLE 2 Lesson Plan Parameters Lesson Plan Name: “Solid Rallying” PlayMode: “Drill” Voice: Default Calculation/Notification Parameters TennisEvent Calculations Notifications My Shot Tally Shot Count: On Announce:{“recover and Record Swing Speed: On split,” “keep feet moving”}; RecordImpact Point: Off Delay: 0.25 secs; Order: Random; Frequency: Every 3rdshot; Opponent's Tally Shot Count: On Announce: {“step into Shot shot,”“80% power”}; Delay: 0.25 secs; Order: Default; Frequency: Randomlyevery 3 shots; End of Announce: {Shot Count, None Exchange Avg. SwingSpeed, Avg. number of steps between shots}; Delay: 0 secs Order:Default; Frequency: Every time Start of Reset Shot Count: On NoneExchange

In an embodiment, Calculations and Notifications may also be configuredto execute instantaneously upon the occurrence of a Tennis Event, orthey may be configured to execute according to a predefined and/oruser-configurable amount of delay. For example, a Notification that isintended to instruct a player on his or her next shot may execute Nseconds after the current shot, where N is a user-configurable number ofseconds and/or partial seconds. In an embodiment, the inventionautomatically adjusts the amount of the delay based on a calculatedmetric of the average time between shots. In this manner, the inventionwill automatically adapt to tennis players of all skill levels.

In an embodiment where more than one Calculation and/or Notification isconfigured to execute with a particular phase, the player may configurethe order in which the Calculations and/or Notifications execute. Theorder can be randomized or fixed. In an embodiment, only a subset of theavailable Calculations and/or Notifications associated with a particularphase is executed, the subset being selected randomly (e.g., select twoout of an available ten) and/or according to a schedule (e.g., wheresome Calculations and/or Notifications are executed every Nth time). Inthis manner, the player may receive a variety of coaching feedback,thereby allowing him or her to focus on multiple areas of improvement.

FIG. 4 illustrates FSM 400 for a Point Mode embodiment. Phases 402, 406,408, 410, and 414 may be associated with one or more Calculations and/orNotifications as discussed above. FSM 400 enters phase 402 (a readystate or starting state) with the occurrence of a Start of Point (“SOP”)Tennis Event. At decision 404, FSM 400 transitions to phase 406 (aservice state) upon the occurrence of a My Shot Tennis Event or phase408 (a receiving state) upon the occurrence of an Opponent's Shot TennisEvent. From either of phases 406 or 408, FSM 400 enters phase 410 (arallying state) upon the occurrence of a My Shot or Opponent's ShotTennis Event.

FSM 400 repeats phase 410 each time a My Shot or Opponent's Shot TennisEvent occurs at decision 412, and enters phase 414 (end of rally) if anEnd of Point (“EOP”) Tennis Event occurs at decision 412. FSM 400 thenloops back to phase 402 with the occurrence of an SOP Tennis Event.

Coaching device 100 may be used in single-user embodiments or multi-userembodiments. In single-user embodiments, Tennis Events at a singlecoaching device 100 drive a corresponding FSM such as FSM 300. Eachstate in FSM 300 may be triggered by Tennis Events at a single coachingdevice 100.

In multi-user embodiments, each coaching device 100 maintains its ownFSM (e.g., a FSM 300 or FSM 400), but the FSM may be affected by TennisEvents at other coaching devices 100. For example, two coaching devicesmay each be executing FSM 400, and both begin in the ready phase 402.When a My Shot Tennis Event occurs at one coaching device 100, it willwirelessly transmit the My Shot Tennis Event to the other coachingdevice 100 (e.g., via its transceiver 210) where it will be received andinterpreted as an Opponent's Shot Tennis Event. In other words, eachcoaching device 100 transmits each Tennis Event to each other coachingdevice 100, thereby ensuring that the FSMs at each coaching device 100are synchronized.

In an embodiment, Tennis Events are transmitted in the form of messages,and each message includes an identification of the coaching devicetransmitting the message along with information about the Tennis Event.Such information may include the type of Tennis Event (e.g., a “My Shot”Tennis Event) as well as information about the type of shot (e.g.,speed, spin, direction, etc.). For example, a coaching device 100 maydetermine that a player hit a forehand lob shot based on the speed anddirection of the shot (e.g., as measured by sensor 204), and thecorresponding message may include this information, thereby enabling areceiving coaching device 100 to generate a relevant Notification (e.g.,an announcement to prepare for an overhead shot).

In alternative embodiments, messages may include measurement informationgathered directly from sensor 204 and/or information about a PhysicalEvent instead of or in addition to information about the Tennis Event.In such embodiments, the receiving coaching device 100 translates themeasurement information into Physical Events and derives correspondingTennis Events in the same manner as the transmitting device.

In multi-user embodiments, coaching device 100 may also operateaccording to a singles player mode or a doubles player mode. Forexample, two opponents in a singles match may each configure theirrespective coaching devices 100 to operate in a singles player mode,meaning alternating shots are expected by the FSM (e.g., a My ShotTennis Event followed by an Opponent's Shot Tennis Event). Two teammatesin a doubles match, on the other hand, may each configure theirrespective coaching device 100 to operate in a doubles player mode,meaning that only one shot per team is expected by the FSM. For example,when two teammates are operating coaching devices 100 in a doublesplayer mode, the FSM 400 at each coaching device 100 will recognize a MyShot Tennis Event regardless of which player hits the ball.

In multi-user embodiments, two or more coaching devices 100 establish acommunication session using a conventional “handshake” or other suitablediscovery/connection mechanism. For example, a player using one coachingdevice 100 may initiate a discover function at coaching device 100 thatseeks out other coaching devices 100 broadcasting their availability.Password authentication or other suitable mechanisms may be employed toensure that only authorized coaching devices 100 may join acommunication session.

FIGS. 5A and 5B respectively illustrate a single-user method 500 and amulti-user method 520 for providing feedback in accordance with thepresent invention. Method 500 begins at step 502. A player may, forexample, initiate method 500 by powering on his or her coaching device100 and selecting a drill or point mode. At step 504, coaching device100 measures values obtained from sensor 204 and calculates one or morephysical parameters (e.g., parameters corresponding to the positionand/or motion of the player's racket). At step 506, coaching device 100translates the physical parameters into a Physical Event (e.g., a swingof a racket or an impact with a ball). At step 508, coaching device 100determines a Tennis Event (e.g., the start of a point) based on thePhysical Event in the previous step. At step 510, coaching device 100determines a corresponding state (e.g., a rallying state) in a model(e.g., a finite state machine) of a drill or point based on the TennisEvent in the previous step. At step 512, coaching device 100 determinescoaching feedback (e.g., a Notification and/or a Calculation) thatcorresponds to the determined state in the previous step. At step 514,coaching device 100 outputs the coaching feedback (e.g., via one or moreof audible, visual, and haptic feedback). Finally, if the playerfinishes a drill or game or wishes to switch to a different mode, method500 ends at step 516. Otherwise, method 500 returns to step 504.

Method 520 begins at step 522. As with method 500, a player may, forexample, initiate method 520 by powering on his or her coaching device100 and selecting a drill or point mode. At step 524, coaching device100 either detects a local event (e.g., an event detected at theplayer's racket) or a remote event (e.g., an event received from theplayer's opponent). For local events, at step 526, coaching device 100measures values obtained from sensor 204 and calculates one or morephysical parameters (e.g., parameters corresponding to the positionand/or motion of the player's racket). Then, at step 528, coachingdevice 100 translates the physical parameters into a Physical Event(e.g., a swing of a racket or an impact with a ball). At step 530,coaching device 100 determines a Tennis Event (e.g., the start of apoint) based on the Physical Event in the previous step. At step 532,coaching device transmits an event message based on the Tennis Event toanother embodiment of the invention.

For remote events, at step 534, coaching device 100 receives an eventmessage from another embodiment of the invention. At step 536, coachingdevice 100 determines a Tennis Event (e.g., the start of a point) basedon the event message received in the previous step.

For both local and remote events, at step 538, coaching device 100determines a corresponding state (e.g., a rallying state) in a model(e.g., a finite state machine) of a drill or point based on the TennisEvent in one of step 532 or step 536. At step 540, coaching device 100determines coaching feedback (e.g., a Notification and/or a Calculation)that corresponds to the determined state in the previous step. At step542, coaching device 100 outputs the coaching feedback (e.g., via one ormore of audible, visual, and haptic feedback). Finally, if the playerfinishes a drill or game or wishes to switch to a different mode, method520 ends at step 544. Otherwise, method 520 returns to step 524.

As illustrated in FIG. 1C, embodiments of coaching device 100 mayinterface with a ball machine 116. In such an embodiment, one or moreplayers with coaching devices 100 may practice with a ball machine 116as if they were playing or practicing with a human opponent or coach. Acoaching device 100 connected to a ball machine 116 maintains an FSM inthe same manner as a coaching device 100 used by a player. In essence, acoaching device 100 connected to a ball machine can be thought of as acoaching device 100 used by another player in a multi-user embodiment,i.e., it transmits and receives messages concerning Tennis Events andother related information, and such Tennis Events drive a correspondingFSM. The primary difference is that Notifications trigger actions at theball machine (e.g., launching the next ball) instead of outputtingcoaching feedback.

For example, a player with a coaching device 100 may initiate a Start ofExchange Tennis Event by hitting her racket with her hand three times.The player's coaching device 100 will then transmit the Start ofExchange Tennis Event to the ball machine's 116 coaching device 100where a corresponding Notification will trigger the ball machine 116 tolaunch a ball. A rally between the player and the ball machine 116 maythen proceed according to an FSM (e.g., FSM 400), with each of theplayer's shots being interpreted as an Opponent's Shot Tennis Event andtriggering a Notification and subsequent launch of another ball at ballmachine 116.

Various parameters at ball machine 116 may be user-configured orestablished in pre-defined lesson plans designed for ball machine 116.For example, ball machine 116 may be configured to launch balls withvarying speed, spin, direction, delay, etc. according to the selectedLesson Plan.

Similar to multi-user embodiments, a player with a coaching device 100establishes a communication session with ball machine 116 using aconventional “handshake” or other suitable discovery/connectionmechanism. The player may also use her coaching device 100 to configureball machine 116 and/or control other aspects of ball machine 116.

In an embodiment, Tennis Events derived by coaching device 100 may alsoor alternatively be communicated to an observer, for example a coachwith a tablet, computer, or mobile device running an application andcommunicating with coaching device 100 via transceiver 210. As withmulti-user and ball machine embodiments, Tennis Events are communicatedvia messages and may be accompanied by other information such asmetrics. Such an embodiment enables an observer to review metrics andother information about the player in real-time. In the same or analternative embodiment, a coaching device 100 may receive real-timeNotifications and/or Calculations from the observer. For example, theobserver may select one or more Notifications using the application onhis or her device for transmission to coaching device 100, which maythen execute the Notifications immediately or at a time determined by aLesson Plan.

In the same or an alternative embodiment, the observer may speak into amicrophone on his or her device, and the observer's voice will betransmitted to coaching device 100 for immediate announcement or at atime determined by a Lesson Plan. Such an embodiment, for example,permits a coach to instruct a player from a distance without having toshout and potentially disturb others. Similarly, in an embodiment, theplayer may speak into a microphone included in or connected to interface202 in coaching device 100, and the player's voice may be transmittedvia transceiver 210 to the observer and/or another player. For example,coaching device 100 may be configured to record and transmit a player'svoice in response to the player pressing a button on coaching device 100or speaking a voice command. In this manner, coaching device 100 may actas a two-way radio, thereby permitting players to communicate with otherplayers and coaches without having to shout.

In an embodiment, players may also speak voice commands to interact withball machine 116. In such an embodiment, interface 202 receives thevoice commands and transmits them via transceiver 210 to the coachingdevice 100 connected to the ball machine 116. The coaching device 100 atthe ball machine 116 may then instruct the ball machine accordingly. Forexample, a player may command the ball machine 116 to launch a shot or aparticular type of shot, or to stop launching shots altogether inaccordance with a selected Lesson Plan.

In an embodiment, Tennis Events may be communicated to other types ofdevices. For example, coaching device 100 may communicate a Tennis Eventmessage to a camera that is programmed to take pictures or video of theplayer upon the occurrence of certain Tennis Events.

The majority of the foregoing description is directed to a tennisembodiment, but other embodiments are also contemplated. For example,the invention could be used in other paddle/racket sports (e.g., tabletennis, racketball, badminton, etc.). The invention could also be usedwhen practicing or playing sports involving a club or stick (e.g., golf,baseball, cricket), whereby the coaching device 100 is secured to orintegrated within some portion of the club or stick, or worn on the bodyof the player, and provides feedback to the player. Such otherembodiments operate in the same fashion as the tennis embodiment, exceptthat events are logically tied to aspects of the corresponding sport.

The present invention can be realized in hardware or a combination ofhardware and software. The invention can be realized in a centralizedfashion in one system, or in a distributed fashion where differentelements are spread across several interconnected systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suitable. A typical combination of hardware andsoftware can be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the system suchthat it carries out the methods described herein.

The present invention, as already noted, can be embedded in a computerprogram product, such as a computer-readable storage medium or devicewhich when loaded in a computer system is able to carry out thedifferent methods described herein. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. It will be appreciatedthat modifications, variations and additional embodiments are covered bythe above teachings and within the purview of the appended claimswithout departing from the spirit and intended scope of the invention.Other logic may also be provided as part of the exemplary embodimentsbut are left out here so as not to obfuscate the present invention.Since modifications of the disclosed embodiments incorporating thespirit and substance of the invention may occur to persons skilled inthe art, the invention should be construed to include everything withinthe scope of the appended claims and equivalents thereof.

The invention claimed is:
 1. A system, comprising: a first wearablecoaching device worn on a first tennis player's wrist; a second wearablecoaching device worn on a second tennis player's wrist; wherein each ofthe first and second wearable coaching devices comprise: at least onesensor; at least one wireless transceiver; at least one interface; atleast one processor; and at least one memory; and wherein each of thefirst and second wearable coaching devices are configured to: detect,using the at least one sensor, a local impact of a tennis ball strikinga tennis racket; transmit, using the at least one wireless transceiver,a message indicative of the local impact to the other coaching device ofthe first and second wearable coaching devices; receive, using the atleast one wireless transceiver, the message from the other coachingdevice of the first and second wearable coaching devices; receive, usingthe at least one interface, player input to select a lesson plan fromamong a plurality of lesson plans stored in the at least one memory,wherein each of the plurality of lesson plans is associated with aplurality of recorded voice messages, and wherein each of the pluralityof recorded voice messages instructs at least one of the first tennisplayer and the second tennis player to perform a tennis action; inresponse to at least one of detecting the local impact and receiving themessage, determine, using the at least one processor, a recorded voicemessage from the plurality of recorded voice messages based on theselected lesson plan; and output, using the at least one interface, thedetermined recorded voice message.
 2. The system of claim 1, wherein theat least one processor determines the recorded voice message from theplurality of recorded voice messages according to a random order.
 3. Thesystem of claim 1, wherein the at least one processor determines therecorded voice message from the plurality of recorded voice messagesaccording to a fixed order, and wherein the order is defined by theselected lesson plan.
 4. The system of claim 1, wherein the at least oneprocessor determines the recorded voice message from the plurality ofrecorded voice messages based on whether the local impact occurred atthe first or second coaching device.
 5. The system of claim 1, whereinone or more of the plurality of recorded voice messages was recorded bythe first tennis player or the second tennis player.
 6. The system ofclaim 1, wherein each of the plurality of lesson plans is associatedwith its own unique set of recorded voice messages.
 7. A wearablecoaching device that is worn on a tennis player's wrist and providesreal-time coaching instructions to the tennis player, comprising: atleast one sensor; at least one wireless transceiver; at least oneinterface; at least one processor; and at least one memory; wherein thewearable coaching device is configured to: detect, using the at leastone sensor, a local impact of a tennis ball striking a tennis racket;transmit, using the at least one wireless transceiver, a first messageindicative of the local impact to at least one other wearable coachingdevice; receive, using the at least one wireless transceiver, a secondmessage from the at least one other wearable coaching device; receive,using the at least one interface, player input to select a lesson planfrom among a plurality of lesson plans stored in the at least onememory, wherein each of the plurality of lesson plans is associated witha plurality of recorded voice messages, and wherein each of theplurality of recorded voice messages instructs the tennis player toperform a tennis action; in response to at least one of detecting thelocal impact and receiving the second message, determine, using the atleast one processor, a recorded voice message from the plurality ofrecorded voice messages based on the selected lesson plan; and output,using the at least one interface, the determined recorded voice message.8. The wearable coaching device of claim 7, wherein the at least oneprocessor determines the recorded voice message from the plurality ofrecorded voice messages according to a random order.
 9. The wearablecoaching device of claim 7, wherein the at least one processordetermines the recorded voice message from the plurality of recordedvoice messages according to a fixed order, and wherein the order isdefined by the selected lesson plan.
 10. The wearable coaching device ofclaim 7, wherein the at least one processor determines the recordedvoice message from the plurality of recorded voice messages based on thelocal impact or the received second message.
 11. The wearable coachingdevice of claim 7, wherein one or more of the plurality of recordedvoice messages was recorded by the tennis player.
 12. The wearablecoaching device of claim 7, wherein each of the plurality of lessonplans is associated with its own unique set of recorded voice messages.13. A method implemented on a wearable coaching device for providingreal-time coaching instructions to a tennis player, comprising:detecting, by a first wearable coaching device, a local impact of atennis ball striking a tennis racket; wirelessly transmitting a firstmessage indicative of the local impact from the first wearable coachingdevice to a second wearable coaching device; receiving, by the firstwearable coaching device, a second message from the second wearablecoaching device; receiving, by the first wearable coaching device,player input to select a lesson plan from among a plurality of lessonplans stored in the first wearable coaching device, wherein each of theplurality of lesson plans is associated with a plurality of recordedvoice messages, and wherein each of the plurality of recorded voicemessages instructs the tennis player to perform a tennis action; inresponse to at least one of detecting the local impact and receiving thesecond message, determining, by the first wearable coaching device, arecorded voice message from the plurality of recorded voice messagesbased on the selected lesson plan; and outputting, by the first wearablecoaching device, the determined recorded voice message.
 14. The methodof claim 13, further comprising determining, by at least one processor,the recorded voice message from the plurality of recorded voice messagesaccording to a random order.
 15. The method of claim 13, furthercomprising determining, by at least one processor, the recorded voicemessage from the plurality of recorded voice messages according to afixed order, and wherein the order is defined by the selected lessonplan.
 16. The method of claim 13, further comprising determining, by atleast one processor, the recorded voice message from the plurality ofrecorded voice messages based on the local impact or the received secondmessage.
 17. The method of claim 13, wherein one or more of theplurality of recorded voice messages was recorded by the tennis player.18. The method of claim 13, wherein each of the plurality of lessonplans is associated with its own unique set of recorded voice messages.